Recovery of nitrogen bases



Jan- 26, 1943- s. H. M ALLISTER ET AL 2,309,324

' RECOVERY OF NITROGEN BASES Filed Feb. 23, 1940 Exrracfed Disfillme Benzene EXTRACTOR 3 2 ST|LL Pefrcfleum Dis I fillafe confain'mq ,Leqn Add 22 24 Nitrogen Bases N'urroqen HEATER /6 I Ems 7 )[H5 IO; Fa? Acid CONDENSER- ,STI ZIPPER 2O COOLEI2- '12 3mm I. Nitrogen bases lnvemors: Seayer A. boHqrd Sumner twister BL; 1*heir Afiorneg: 1:{ 6; L

Patented Jan. 26, 1943 N UNITED STATES PATENT OFFICE RECOVERY OF NITROGEN BASES Sumner H. McAllister, Lafayette, and Beaver A. Ballard, Berkeley, Calif., assig'nors to Shell Development Company, San Francisco, Calif., a corporation of Delaware Application February 23,1910, Serial No. 320,444 10 Claims. (of. 260-290) This invention relates to a process for removhydrocarbon oils or gases, by contacting such ing nitrogen bases from water-insoluble organic substances with aqueous solutions of certain solvents, mineral oil, hydrocarbon fractions, etc.. weak acids having dissociation constants below It has long been known that nitrogen bases about l and preferably of the order of about can be extracted from hydrocarbons and the like 5 to 10- under conditions to form two fluid by employing extracting agents such as strong phases, at least one of which is liquid and commineral acids, e. g., sulfuric acid, hydrochloric prises a fat aqueous solution containing the acid acid, etc. The nitrogen bases combine with the and absorbed nitrogen bases, and the other which acids to form sulfates, chlorides, etc., as the case isliquid or vaporous and consists essentially of may be. Inorderv to recoverthe bases it isnec- 10 the organic substance from which at least a'poresary to displace them from their salts by treattion of the nitrogen bases have been removed. ing with stronger bases such as sodium hydrox- The two phases are separated and the fat acid ide, calcium hydroxide, etc., whereby the nitrosolution is then stripped with steam or other gen bases are liberated and maybe separated by inert hot convection medium such as gaseous decantation, scrubbing, .etc. hydrocarbons or an organic solvent having good This process has certain disadvantages. solvent properties for the nitrogen bases. The Strong acids tend to polymerize unsaturated nitrogen bases may then be recovered from the hydrocarbons which are frequently presentin stripping medium by fractional condensation or petroleum distillates, to form gums, resins, etc.,- distillation, as the case may require. and also tend to extract from thedistillates con- We have discovered that aqueous solutions of stituents which because of their anti-knock certain weakly acidic substances make very satproperties can more advantageously be left in isfacbo y e t a t n agents 0111 P o s distillates which are intended for motor fuel. Acids suitable in our process fall into several Moreover, large quantitiesof chemicals are concategories. We prefer to employ organic carsumed because the strong acids and bases 'canboxylic acids in our process although certain innot be regenerated conveniently from the resultorganic acids including acid salts are suitable. ing salts which are formed. The organic acids may be mono or polycar- Liquid 80: ha been employed to remove nitroboxylic. In general substituted organic carboxgen bases'from petroleum distillates but it suffers ylic acids are preferable since unsubstituted the disadvantage of removing at the same time 80 mono carboxylic organic acids usually have the aromatic constituents. Therefore, to prepare disadvantage of forming azeotropes which boil nitrogen bases by the SO: process, an additional below the boiling temperature of water and/or separation from the aromatics is necessary. are too-insoluble in water to make satisfactory It is an object of our invention to provide a extracting agents. or the substituted organic process which allows the regeneration of the $5 acids the hydroxy c o ylic and polycarboxy lc extracting agents for repeated use. This enables acids are in general preferable, but in many cases theeccnomical use of extracting agents which halogenated acids and keto acids may be cmare often relatively expensive. Another object ployed as well. Sometimes in dealing with keto is the production-of nitrogen bases. in a concenacids special precautions must be employed to trated form in which they can be used for various 4o avoid the decomposition of these substances. Purposes. For example the nitrogen bases pro- Examples of suitable hydroxy acids are lactic duced by our process can be fractionated by acid, mandelic acid, malic acid, glycollic acid, simple distillation to furnish raw materials for etc. Suitable polycarboxvlic acids are citric, the manufacture of dyes, wetting agents, rubber tartaric, glutaric, methyl succinic, ethyl succinic, accelerators and other valuable organic chemdiglycollic, etc. Suitable halogenated acid: are icals. Still a further object is the removal 01' brom-acetic, chlor-acetic. alphar -p o ni nitrogen bases from hydrocarbon oils for puralpha chlor prcpionic, beta broin propionic, poses of purifying them, since it is known that beta-chlor-propionic acid. Keto acids which these substances sometimes impart harmful may be used are laevulinic acid, pyruvic acid properties to hydrocarbon oils intended for variand thelike.

ous uses. For example, they impart an unpleas- Certain organic acids which would be too out odor to gasoline or kerosene. strong as extracting agents if employed by them- Our process comprises extracting nitrogen selves can still be used if they are suitably modibases from their solutions in organic waterfled. For example oxalic acid may be partially insoluble normally fluid substances, such as 5 neutralized with a strong base to give for example mono-sodium oxalate which is a suitable agent for our process. Certain inorganic acids may also be employed, for example. boric acid used preferably in conjunction with glycerin, phosphorous acid, or the products of partial neutralization of certain stronger acids such as mono sodium or potassium dihydrophosphate, etc. While the choice of the most suitable acid will to some extent depend on the particular about 10- to It is preferable that the'acids shall not form azeotropes with water which boil below the boiling temperature of water to avoid losses of the acids during stripping andto prevent contamination of the liberated nitrogen bases; and moreover the acids must be sufliciently stable so as not to decompose appreciably under the conditions of extraction and stripping. The acids must be of such reactivity that. they do not readily undergo polymerization, condensation, etc., i.- e., their reactivities must be limited to salt formation only under the conditions of the process. We have found that acids of this strength arestrong enough to efficiently extract nitrogen bases from their solutions in waterinsoluble organic solvents and on the other hand are weak enough so that their salts hydrolyze with nitrogen bases at moderately elevated temperatures under the conditions of our process, to enable regeneration by stripping methods. Acids having dissociation constantsof 10- and higher form salts with nitrogen bases which cannot normally be separated by stripping methods.

These acids are all relatively easily purified. This property isv an advantage since occasionally tarry asphaltic substances and other impurities accumulate in the extracting solutions which are used over long periods of time in the regenerative extraction cycle of this invention.

Moreover, these acids are such that their aqueous solutions under the conditions of our process cause little or no corrosion of many standard metals ordinarily used in equipment construc- I tion.

The amount of aqueous acid solution required in the extraction is normally above 5% of the hydrocarbon phase by volume and for economical reasons seldom exceeds about 100% by volume. Normally from. 10 to 50% by volume is used depending upon the required thoroughness of removing the nitrogen bases.

The concentration of acid in the aqueous solution is preferably between about 15% by weight and 90% of saturation at the temperature of extraction. Usually it is not desirable to use a more concentrated solution because some solutions approaching saturation tend to deposit crystals of acid from solution when temperature fluctuations occur thus causing the clogging of pipes and other operating difficulties. 0n the other hand if the concentration of the acid is below about 10 or 15% by weight, there is danger of poor and incomplete extraction of the nitrogen bases from their solutions in the organic water-insoluble liquids.

In general we prefer to carry out the extraction at ordinary atmospheric temperatures,

though it may at times be advantageous to maintain during the extraction a slightly elevated temperature to adjust the solubility relationships between the acid and .water and the substance being extracted. Thus extraction temperatures between 0 and 60 C. may conveniently be employed.

Regeneration may be effected by reversing the extraction, 1. e., by stripping the fat aqueous solution containing the absorbed nitrogen bases in the form of their salts with the acids, at a temperature sufficiently high to cause a substantial increase in the hydrolysis of the nitrogen base salts. Normally, it is desirable to go to temperatures of C. and higher and preferably C. and above, if necessary under superatmospheric pressure. The stripping may be carried out by means of a vaporous or liquid convection or stripping medium. Of the vaporous media, steam is preferred, although other substantially inert gases as air, flue gas, hydrocarbon gas, nitrogen, etc., may also be used. Suitable liquid media are those which are substantially neutral, ties for the nitrogen bases, are substantially insoluble in water, are stable under the conditions of the strippin and have boiling temperatures sufliciently above or below the boiling temperature of the nitrogen bases to enable their separation from the latter by simple fractional distillation. Examples are low-boiling hydrocarbons, as liquid propane, butane, pentanes, hexanes, benzene,- toluene, xylenes, kerosene, gas oil; chlorinated hydrocarbons as carbon tetrachloride, chlormethane, chlorethane, chlorpropane, ethylene dichloride, trichlorethylene; alcohols, simple ethers or ketones of 5 or 6 or more carbon atoms; nltrobenzene, etc.

Our process is particularly applicable to the .ance with our invention are those which are substantially neutral, are substantially insoluble in water, and are stable under the conditions of the extraction. For example, various hydrocarbon liquids, chlorinated hydrocarbon liquids, and in general all those liquids enumerated to be suitable for liquid stripping media may be extracted by our process. If the extraction is accomplished by liquid-liquid contact, which in general is preferable, the organic substances need not be vaporizable. On the other hand a vapor-liquidextraction is predicated on low boiling temperatures of the organic substance as well as of the nitrogen bases.

The attached drawing represents a flow diagram of one embodiment of our process. A petroleum distillate, containing nitrogen bases is admitted through line I to the bottom of extractor wherein it is contacted with a lean aqueous solution of lactic acid admitted to extractor through line 3. The treated hydrocarbon distillate after contact passes from the top of extractor 2 through line 4 to storage not shown. The lactic acid solution which extracts nitrogen bases in the extractor 2. thus becoming have good solvent proper-q i'at," passes from the bottom of extractor 2 through line 5 to heater 8, whence it is admitted through line I to strippe 8.

The stripper can be operated with liquid or vapor stripping media, as explained before. If a vapor such as steam is used'valves H and I5 are closed and valve I8 is open as is valve I3 to admit steam from a source not shown to stripper 8 via line 8. This causes vaporization of the nitrogen base leaving a lean acid solution stripped of most of the nitrogen bases. The lean acid solution passes from the bottom of stripper 8 through line I I to cooler l2, whence it is recirculated to the top of extractor 2 through line 8. The vaporized nitrogen bases and steam pass from the top of stripper 8 through line ill to condenser I! and on through line I 8 to separator 19 wherein the aqueous layer and nitrogen base layers separate into two liquid phases. The nitrogen base layer is withdrawn via line 20 to storage not shown and the aqueous layer may be withdrawn via line 2|. This layer may be treated with a neutral inorganic salt to salt. on further amounts of dissolved nitrogen bases. or it may be employed-to make steam for use in the process.

If a liquid stripping medium such as benzene is used, valves 13 and i 8 are shut and valves H and I5 are open. In this case the extraction and stripping stages of the process are the same as when steam stripping is employed except that hot benzene is admitted to stripper 8 from line 28 through valve 14 and line 8. The temperaturesin the extractor and stripper are regulated so that the hydrolysis of the nitrogen base salts is materially greater in stripper 8 than in the extractor 2. The nitrogen bases thus liberated readily dissolve in the benzene solvent and leave behind a lean aqueous. acid solution. The lean solution is recirculated to extractor 2 as before through line 8. The benzene containing nitrogen bases passes from. the top of stripper 8 via lines in and 22 to still 23 which is heated by coil 24. Benzene being more volatile than the nitrogen bases normally associated with petroleum distillates, is distilled oil and passes as vapor through line 26 to condenser 21 and thence returns to stripper 8 through lines 28 and 8. The less volatile nitrogen bases are withdrawn from the bottom of still 23 via line to storage not shown.

It is understood that the-above description is but one embodiment of the present invention. The use of pumps, auxiliary heat exchangers, coolers, condensers, by-passes, etc., willnt once be evident to those skilled in the design of extraction and rectifying equipment.

The following examples further illustrate the invention:

Example I A cracked stove oil fraction of pressure distillate from California petroleum was treated in athree-stage countercurrent extractor with 20% lactic acid, using a volume ratio of cracked stove oil tolactic acid equal to 20:1. The entering cracked stove oil fraction contained 0.55 volume per cent of nitrogen bases, while the exit cracked stove oil contained only 0.055 volume per cent nitrogen bases. This corresponds to a 90% recovery of bases from the cracked stove oil. The lactic acid containing nitrogen bases was then treated with benzene at 150 C. in a second threestage countercurrent extractor, using a volume ratio of benzene to acid equal to 2:1. The feed contained 10.1 gallons of nitrogen bases per 100 gallons of 20% lactic acid, while the extracted acid contained only 2.2 gallons of nitrogen bases per gallons of 20% lactic acid. This corresponds to a 78% recovery of nitrogen bases from the lactic acid. The extracted acid was then returned to the first countercurrent extractor for further extraction purposes. The resulting tat benzene containing the nitrogen bases was fractionally distilled, separately to recover the two components.

Example 11 Third cut cracked gasoline containing'0.25 volume per cent nitrogen bases was treated in the same manner as described in the previous example. Ninety per cent recovery or nitrogen bases from the gasoline was obtained using a threestage extractor with a 40:1 ratio of hydrocarbon to acid. The 20% lactic acid containing nitrogen bases was then treated with superheated steam under pressure, whereupon most of the nitrogen bases were removed as a water azeotrope while the regenerated lactic acid was returned to the countercurrent extractor for further use. The azeotrope was condensed, whereupon it separated into two layers: water and nitrogen bases.

' We claim as our invention;

1. In a process for removing basic components consisting of nitrogen bases from an organic substantially water-insoluble, normally fluid substance containing them, the steps of contacting said substance with an acidic aqueous solution containing a substantial amount 01 an acidic component which consists essentially of at least one acid having a dissociation constant below 10' and greater than 10', which acid is stable under the conditions of the process, does not form an azeotrope with water which boils below the boiling temperature of water, is substantially soluble in water and is substantially insoluble in said water-insoluble substance, under conditions to form two fluid phasea at least one of which is a liquid aqueous phase containing absorbed nitroen bases, and .the other phase consisting essentially oi the contacted organic substance, separating said phases, stripping said separated aqueous phase with steam under conditions to take said nitrogen bases overhead and to leave said acidic component in the residual stripped aqueous phase, and recirculating the latter to contact further amounts of said substance.

. 2. In a process for removing basic components consisting oi nitrogen bases from an organic substantially water-insoluble, norm-ally fluid substance containing them, the steps of contacting said substance with an aqueous solution of lactic acid, under conditions to form two fluid Phases, at least one of which is a liquid aqueous phase containing absorbed nitrogen bases, and the other phase consisting essentially of the resulting contacted organic substance, separating said phases, stripping said separated aqueous phase with steam under conditions to take said nitrogen bases overhead and to leave said lactic acid in the residual aqueous phase, and recirculating the latter to contact further amounts of saidv substance.

. 3. In a process for removing petroleum nitrogen bases from an organic substantially watersubstance, separating said phases, strippins said separated aqueous phase with steam under conditions to take said nitrogen bases overhead and to leave said glutaric acid in the residual aqueous phase, and recirculating the latter to contact further amounts of said substance.

4. In a process for removing basic components consisting of nitrogen bases from an organic substantially water-insoluble, normally fluid sub, stance containing them, the steps of contacting said substance with anaqueous solution of citric acid, under conditions to iorm two fluid phases, at least one of which is a liquid aqueous phase containing absorbed nitrogen bases, and the other phase consisting essentially of the contacted organic substance, separating said phases, stripping said separated aqueous phase with steam under conditions to take said nitrogen bases overhead and to leave said citric acid in the residual aqueone phase, and recirculating the latter to contact further amounts of said substance.

5. In a process for removing basic components consisting of petroleum nitrogen bases from a mineral oil containing them, the steps of contacting said mineral oil with an acidic aqueous solution containing a substantial amount of an acidic component which consists essentially of at least one acid having a dissociation constant below 10- and greater than 10", which acid is stable under the conditions of the process, does asoaaaa not form an azeotrope with water which boils below the boiling temperature or water, is substantially soluble in water and is substantially insoluble in said mineral oil, under conditions to form two fluid phases, at least one of which is a liquid aqueous phase containing absorbed nitrogen bases, and the other phase consistin essentially of the contacted mineral oil, separatme said phases, stripping said separated aqueous Phase with steam under conditions to take said nitroaen bases overhead and to leave said acidic component in the residual aqueous phase, and recirculating the latter to contact i'urther amounts of said mineral oil;

6. The process of claim 1 wherein said nitrogen bases are organic nitrogenbases.

7. The process of claim 1. wherein the acid in said solution has a concentration rromabout 15% by weight to 90% saturation under the conditions of said contact.

8. The process or claim 1 wherein the organicsubstance is contacted with from 5% to 100% of its own volume of the aqueous acid solution. 9. The process of claim 1 wherein the acid is a hydroxy carboxylic acid.

10. The process or! claim 1 wherein the acid is a polycarboxylic acid.

SUMNER H. MCAILIS'I'ER. SEAVER A. BALLARD. 

